[Greasemonkey] Basic JavaScript questions

[mmccarthy at reifysoft.com]

> As mentioned in an earlier message, getElementsByTagName
> is a dynamic array, not a static snapshot.

Whoops, I didn't know that the *returned value* is dynamic.  So there's no
difference between the following, either in functionality or efficiency?
(Never mind that they won't do what the OP wants.)

1)
var elements = document.getElementsByTagName("h3");
for (var i = 0; i < elements.length; i++)
{
  elements[i].parentNode.removeChild(elements[i]);
}

2)
for (var i = 0; i < document.getElementsByTagName("h3").length; i++)
{
  document.getElementsByTagName("h3")
[i].parentNode.removeChild(document.getElementsByTagName("h3")[i]);
}

Matt McCarthy
When I am king, you will be first against the wall 
With your opinion, which is of no consequence at all. 
-Radiohead, "Paranoid Android" 

-----Original Message-----
From: greasemonkey-bounces at mozdev.org
[mailto:greasemonkey-bounces at mozdev.org] On Behalf Of Mark Pilgrim
Sent: Wednesday, June 29, 2005 1:51 PM
To: greasemonkey at mozdev.org
Subject: Re: [Greasemonkey] Basic JavaScript questions

On 6/29/05, chris feldmann <cfeldmann at gmail.com> wrote:
>  Something about using document.getElementsByTagName() makes it unuseful
for
> this. XPath on the other hand provides an array that can be cleanly
iterated
> through.

As mentioned in an earlier message, getElementsByTagName is a dynamic
array, not a static snapshot.  Which means that the original code is
not only wrong, it's doing a lot of extra work to be wrong
(recalculating the length every time through the loop).

document.evaluate('//h3', document, null,
XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE, null) will return something
that you can iterate through and remove things from without modifying
the original.  (That's what the "SNAPSHOT_TYPE" part means.)  This is
Firefox-specific and will not work in Turnabout/IE or Opera.

Or, as someone else pointed out, you could add a CSS rule "h3 {
display: none ! important }" and not worry about the fact that they're
still in the DOM.

-- 
Cheers,
-Mark
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